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An unexpected cold wave in July 920 sent the people of Baghdad back under their blankets, forcing them to leave their summertime roof beds and go back inside, according to a new study by Spanish researchers. The temperature dropped about 16 degrees F compared to average July temperatures, the study found. That was in 920; there’s no “1” in there.

Arabic historians’ records chronicle life in Baghdad in the Middle Ages, and some of the reports mention the area’s climate. Now scientists have interpreted them for the first time, and found some surprising meteorological events in the areas now known as Iraq and Syria. It used to snow more often, with at least six snowfalls between 902 and 944. (There has been only one snowfall in Baghdad in modern times, on Jan. 11, 2008.) The Arabic historians also recounted droughts, floods, heavy rains and frost, not a common occurrence in the fertile crescent.

The researchers, led by Fernando Domínguez-Castro in the physics department at the University of Extremadura, believe a couple volcanic eruptions in central America could have been to blame for the July 920 cold snap. During some of those nights, temperatures never rose above 64 degrees F — pretty cool for a Baghdad July.

The Guagua Pichincha volcano in Ecuador erupted around 910, and the Ceboruco volcano in Mexico erupted around 930. Eruptions like that have been shown to affect global temperatures. But more evidence is needed to confirm this hypothesis, Domínguez-Castro said.

This is interesting in part because this is a time and a place about which very little is known, the researchers say. But along with their historical significance, these records could help scientists’ understanding of future climates. Knowledge of past trends and abnormalities improves climate models, for instance. Time and again we have seen how old records can paint a fuller picture of our modern lives — in this case, by looking at in the Middle East in the years before the first crusades. The research appears in the journal Weather.

Note, this record took place at the end of a known cold period before the beginning of the Medieval Warming Period. It should have been cooler over a longer period, before this reported incident of a cold July.